Eo ipso means "by the thing itself" in Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 and is similar to the sense expressed by the English idioms, "by the same token," "of itself" or "on its own account". It is often used in various schools of philosophy

Philosophy

Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 to demonstrate the possibility/impossibility of propositions from their nature. For example, That I am does not eo ipso mean that I think. The term is also used in law

Law

Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, and it is through law that it was brought into English from Latin.

In The Crisis and a Crisis in the Life of an Actress

The Crisis and a Crisis in the Life of an Actress

The Crisis and a Crisis in the Life of an Actress was a series of articles written by the Danish philosopher Søren Kierkegaard in 1847 and published in the Danish newspaper Fædrelandet in 1848 under the pseudonym Inter et Inter....

by Søren Kierkegaard

Søren Kierkegaard

Søren Aabye Kierkegaard was a Danish Christian philosopher, theologian and religious author. He was a critic of idealist intellectuals and philosophers of his time, such as Georg Wilhelm Friedrich Hegel, Friedrich Wilhelm Joseph Schelling and Karl Wilhelm Friedrich Schlegel...

, the philosopher describes the quality of Eo ipso in the following excerpt:

But to be gallant towards an artist is precisely the highest degree of insolence, a maudlin impertinence and a disgusting kind of intrusiveness. Anyone who is something, and is something essentially, possesses "eo ipso," the claim to be recognized for exactly this special thing, and for nothing more or less.